Yuhang Wang

Related publications (18)

BigNeuron: a resource to benchmark and predict performance of algorithms for automated tracing of neurons in light microscopy datasets

Pascal Fua, Sean Lewis Hill, Xiang Li, Amos Sironi, Yuhang Wang, Jian Yang, Jian Zhou

BigNeuron is an open community bench-testing platform with the goal of setting open standards for accurate and fast automatic neuron tracing. We gathered a diverse set of image volumes across several species that is representative of the data obtained in many neuroscience laboratories interested in neuron tracing. Here, we report generated gold standard manual annotations for a subset of the available imaging datasets and quantified tracing quality for 35 automatic tracing algorithms. The goal of generating such a hand-curated diverse dataset is to advance the development of tracing algorithms and enable generalizable benchmarking. Together with image quality features, we pooled the data in an interactive web application that enables users and developers to perform principal component analysis, t-distributed stochastic neighbor embedding, correlation and clustering, visualization of imaging and tracing data, and benchmarking of automatic tracing algorithms in user-defined data subsets. The image quality metrics explain most of the variance in the data, followed by neuromorphological features related to neuron size. We observed that diverse algorithms can provide complementary information to obtain accurate results and developed a method to iteratively combine methods and generate consensus reconstructions. The consensus trees obtained provide estimates of the neuron structure ground truth that typically outperform single algorithms in noisy datasets. However, specific algorithms may outperform the consensus tree strategy in specific imaging conditions. Finally, to aid users in predicting the most accurate automatic tracing results without manual annotations for comparison, we used support vector machine regression to predict reconstruction quality given an image volume and a set of automatic tracings. This resource describes a collection of neurons from a variety of light microscopy-based datasets, which can serve as a gold standard for testing automated tracing algorithms, as shown by comparison of the performance of 35 algorithms.

NATURE PORTFOLIO2023

An integrated flexible film as cathode for High-Performance Lithium-Sulfur battery

Rui Guo, Yong Li, Wen Liu, Yuhang Wang, Kangning Zhao

Poor cycling stability and low volumetric capacity of sulfur cathode prevents practical application of Lithium-sulfur (Li-S) batteries. Herein, we demonstrate a strategy to address the two drawbacks of sulfur cathode by synthesizing a compact and flexible film cathode with bilayer structure using a two-step vacuum filtration method. Two layers make up the sulfur cathode, active layer (sulfur-acethlene black (S-C) spheres) and barrier layer (three dimensional MnO2-graphene oxide-multi-walled carbon nanotubes (MnO2-GO-CNTs) composites), which are integrated together by reduced graphene oxide (rGO) through self-binding. The rGO sheets provide an electrical conductive framework and a stable architecture to accommodate volume changes of sulfur. S-C spheres stacked orderly between the rGO layers facilitate fast Li+ storage and energy release. Polar MnO2-GO-CNTs composites with large specific surface area have not only afforded efficient sites for chemically binding polysulfides, but also provided fast electron trans-fer for accelerating polysulfides redox reaction. Consequently, the integrated film cathode exhibits an unprecedented cycling stability of similar to 0.0279% capacity decay per cycle over more than 600 cycles at 1C and high volumetric capacity of 1021.9 Ah L-1 at 2C. Meanwhile, a foldable Li-S battery based on this flexible cathode is fabricated and shows excellent mechanical and electrochemical properties. The integrated flexible sulfur cathode of this study sheds light on the design strategies for application in flexible high volumetric capacity system. (C) 2021 Elsevier Inc. All rights reserved.

ACADEMIC PRESS INC ELSEVIER SCIENCE2022

In situ growth of graphene on both sides of a Cu-Ni alloy electrode for perovskite solar cells with improved stability

Michael Graetzel, Yuhang Wang, Yinghui Wu

The instability of rear electrodes undermines the long-term operational durability of efficient perovskite solar cells. Here, a composite electrode of copper-nickel (Cu-Ni) alloy stabilized by in situ grown bifacial graphene is designed. The alloying makes the work function of Cu suitable for regular perovskite solar cells. Cu-Ni is the ideal substrate for preparing high-quality graphene via chemical vapour deposition, which simultaneously protects the device from oxygen, water and reactions between internal components. To rivet the composite electrode with the semi-device, a thermoplastic copolymer is applied as an adhesive layer through hot pressing. The resulting devices achieve power conversion efficiencies of 24.34% and 20.76% (certified 20.86%) with aperture areas of 0.09 and 1.02 cm(2), respectively. The devices show improved stability: 97% of their initial efficiency is retained after 1,440 hours of a damp-heat test at 85 degrees C with a relative humidity of 85%; 95% of their initial efficiency is retained after 5,000 hours at maximum power point tracking under continuous 1 sun illumination. The instability of contact layers for perovskite solar cells under operating conditions limits the deployment of the technology. Now, Lin et al. develop a Cu-Ni electrode sandwiched between in situ-grown graphene protective layers, enabling solar cells with improved stability under light, humidity and high temperature.

NATURE PORTFOLIO2022

Silica-copper catalyst interfaces enable carbon-carbon coupling towards ethylene electrosynthesis

Michael Graetzel, Yelin Hu, Jun Li, Dan Ren, Xiaoyan Wang, Zishuai Wang, Yuhang Wang, Yi Xu, Reza Zamani

Membrane electrode assembly (MEA) electrolyzers offer a means to scale up CO2-to-ethylene electroconversion using renewable electricity and close the anthropogenic carbon cycle. To date, excessive CO2 coverage at the catalyst surface with limited active sites in MEA systems interferes with the carbon-carbon coupling reaction, diminishing ethylene production. With the aid of density functional theory calculations and spectroscopic analysis, here we report an oxide modulation strategy in which we introduce silica on Cu to create active Cu-SiOx interface sites, decreasing the formation energies of OCOH* and OCCOH*-key intermediates along the pathway to ethylene formation. We then synthesize the Cu-SiOx catalysts using one-pot coprecipitation and integrate the catalyst in a MEA electrolyzer. By tuning the CO2 concentration, the Cu-SiOx catalyst based MEA electrolyzer shows high ethylene Faradaic efficiencies of up to 65% at high ethylene current densities of up to 215mAcm(-2); and features sustained operation over 50h. CO2-to-ethylene conversion using renewable electricity provides a sustainable route to produce valuable chemicals. Here, the authors report high ethylene activity of 215mAcm(-2) and selectivity of 65% made possible by silica clusters in copper.

NATURE RESEARCH2021

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Metal halide perovskite quantum dots (Pe-QDs) are of great interest in new-generation photovoltaics (PVs). However, it remains challenging in the construction of conductive and intact Pe-QD films to maximize their functionality. Herein, a ligand-assisted surface matrix strategy to engineer the surface and packing states of Pe-QD solids is demonstrated by a mild thermal annealing treatment after ligand exchange processing (referred to as "LE-TA") triggered by guanidinium thiocyanate. The "LE-TA" method induces the formation of surface matrix on CsPbI3 QDs, which is dominated by the cationic guanidinium (GA(+)) rather than the SCN-, maintaining the intact cubic structure and facilitating interparticle electrical interaction of QD solids. Consequently, the GA-matrix-confined CsPbI3 QDs exhibit remarkably enhanced charge mobility and carrier diffusion length compared to control ones, leading to a champion power conversion efficiency of 15.21% when assembled in PVs, which is one of the highest among all Pe-QD solar cells. Additionally, the "LE-TA" method shows similar effects when applied to other Pe-QD PV systems like CsPbBr3 and FAPbI(3) (FA = formamidinium), indicating its versatility in regulating the surfaces of various Pe-QDs. This work may afford new guidelines to construct electrically conductive and structurally intact Pe-QD solids for efficient optoelectronic devices.

2020

Efficient Perovskite Solar Cell Modules with High Stability Enabled by Iodide Diffusion Barriers

Michael Graetzel, Yuhang Wang, Tianhao Wu, Xianwei Zeng, Hongwei Zhu

Operational stability of efficient opto-electronic conversion is crucial for the success in large-scale application of perovskites devices. Owing to the intrinsically weak structure of perovskites, iodide represents the most volatile constituents, and its diffusion can induce irreversible degradation that continues to present a great challenge to realize stable perovskite devices, Here, we introduce a low-temperature processing strategy to increase the operational stability of high-efficiency perovskite solar modules by engineering low-dimensional diffusion barriers, reducing the unwanted interfacial diffusion of ions by 10(3)-10(7) times in magnitude. We finally achieved stable and efficient perovskite solar modules with an area of 36 cm(2) retaining over 95% of their initial efficiency of over 15% after 1,000 h of heating at 85 degrees C, and 91% after light soaking in AM 1.5 G solar light for 1,000 h, respectively. Our findings provide an effective strategy to realize operationally stable and efficient perovskite solar cell modules.

CELL PRESS2019

Efficient stable graphene-based perovskite solar cells with high flexibility in device assembling via modular architecture design

Yuhang Wang, Shaik Mohammed Zakeeruddin, Hong Zhang, Chunyang Zhang

Carbon-based perovskite solar cells (C-PSCs) are emerging as low-cost stable photovoltaics. However, their power conversion efficiency (PCE) still lags behind that of devices based on Au or Ag as the current collector. Here, we introduced an innovative modular PSC design using a carbon back electrode, whose sheet resistance and thickness were greatly reduced by covering it with another carbon-coated FTO glass that was applied under pressure. We showed that these two individual elements could be assembled and separated repeatedly. Moreover, among the various commercial carbon sources (carbon black, graphite sheet, and graphene), graphene exhibited the best overall performance, showing the crucial importance of graphene as a charge collector. Power conversion efficiency (PCE) of 18.65% was achieved for graphene-based PSCs (G-PSCs), which was among the highest efficiency reported so far for C-PSCs. Moreover, the optimized devices without encapsulation retained 90% of their initial PCE after aging at an elevated temperature of 85 degrees C for 1000 h. Remarkably, G-PSCs showed significant structural flexibility; there was negligible degradation in PCE after repeated disassembling and assembling for more than 500 cycles. Our system provides a promising prospect for the facile repair and maintenance of PSCs via modular interconnections; related strategies may be extended to other devices.

2019

Thermodynamically stabilized beta-CsPbI3-based perovskite solar cells with efficiencies > 18%

Mohammad Ibrahim Dar, Xingyu Gao, Yang Li, Xiaoyan Wang, Yuhang Wang, Ying Yang

Although beta-CsPbI3 has a bandgap favorable for application in tandem solar cells, depositing and stabilizing beta-CsPbI3 experimentally has remained a challenge. We obtained highly crystalline beta-CsPbI3 films with an extended spectral response and enhanced phase stability. Synchrotron-based x-ray scattering revealed the presence of highly oriented beta-CsPbI3 grains, and sensitive elemental analyses-including inductively coupled plasma mass spectrometry and time-of-flight secondary ion mass spectrometry-confirmed their all-inorganic composition. We further mitigated the effects of cracks and pinholes in the perovskite layer by surface treating with choline iodide, which increased the charge-carrier lifetime and improved the energy-level alignment between the beta-CsPbI3 absorber layer and carrier-selective contacts. The perovskite solar cells made from the treated material have highly reproducible and stable efficiencies reaching 18.4% under 45 +/- 5 degrees C ambient conditions.

AMER ASSOC ADVANCEMENT SCIENCE2019

Recent advances in the use of organic-inorganic hybrid perovskites for optoelectronics have been rapid, with reported power conversion efficiencies of up to 22 per cent for perovskite solar cells1-9. Improvements in stability have also enabled testing over a timescale of thousands of hours(10-14). However, large-scale deployment of such cells will also require the ability to produce large-area, uniformly high-quality perovskite films. A key challenge is to overcome the substantial reduction in power conversion efficiency when a small device is scaled up: a reduction from over 20 per cent to about 10 per cent is found(15-21) when a common aperture area of about 0.1 square centimetres is increased to more than 25 square centimetres. Here we report a new deposition route for methyl ammonium lead halide perovskite films that does not rely on use of a common solvent(1,2,4-15) or vacuum3: rather, it relies on the rapid conversion of amine complex precursors to perovskite films, followed by a pressure application step. The deposited perovskite films were free of pin-holes and highly uniform. Importantly, the new deposition approach can be performed in air at low temperatures, facilitating fabrication of large-area perovskite devices. We reached a certified power conversion efficiency of 12.1 per cent with an aperture area of 36.1 square centimetres for a mesoporous TiO2-based perovskite solar module architecture.

Nature Publishing Group2017

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Autophagy is linked to cell death, yet the associated mechanisms are largely undercharacterized. We discovered that melanoma, which is generally resistant to drug-induced apoptosis, can undergo autophagic cell death with the participation of orphan nuclear receptor TR3. A sequence of molecular events leading to cellular demise is launched by a specific chemical compound, 1-(3,4,5-trihydroxyphenyl)nonan-1-one, newly acquired from screening a library of TR3-targeting compounds. The autophagic cascade comprises TR3 translocation to mitochondria through interaction with the mitochondrial outer membrane protein Nix, crossing into the mitochondrial inner membrane through Tom40 and Tom70 channel proteins, dissipation of mitochondrial membrane potential by the permeability transition pore complex ANT1-VDAC1 and induction of autophagy. This process leads to excessive mitochondria clearance and irreversible cell death. It implicates a new approach to melanoma therapy through activation of a mitochondrial signaling pathway that integrates a nuclear receptor with autophagy for cell death.

Nature Publishing Group2014